@cvp thank you for your help!
Regarding your first message:
I‘m calling the loc_selection function here to get that print(„Segment A“). I want to replace print with a boolean later on to say „Segment A“ selected = True.
Thanks for your advice in your second message! Didn‘t think about that.
Unfortunately I don‘t understand your third message - thats exactly how it‘s set in my UI file.

Currently I‘ve set „list_item_clicked“ as action for my TableView. Thats working so far, but I don‘t know how to differentiate between the rows to call a different function for each of them. Right now my whole TableView is acting like one fat Button with just a single action.

I didn‘t programm for a long time now, and just started with Python last week, because I missed programming and wanted to try something new.
Now after planning my first project, I decided to start with a simple UI, and thought it should be done fairly quick.